May 24 2019
A standard query faced by people when choosing to make their home energy-efficient and green is, should one use gas or electric for the heating and cooling requirements? Gas is the more environmentally friendly option—at the moment—for an energy-efficient home located in Maryland. This conclusion was arrived at in a new economic study by the National Institute of Standards and Technology (NIST), which assessed the power consumption and environmental impact of gas versus electric heating, ventilation, and air conditioning (HVAC) systems in low-energy residential households. The NIST work offers a research technique that others can apply to conduct their own analysis on which technology is more promising for their local regions.
NIST's Net Zero Energy Residential Test Facility in Gaithersburg, Maryland, provided measurements for a NIST analysis of the environmental impacts of gas and electric HVAC systems in energy-efficient Maryland homes. (Image credit: Beamie Young/NIST)
“Fuel type is an important factor because heating and cooling accounts for a significant amount of home energy consumption,” said NIST civil engineer David Webb, one of the authors of the new research, published in the Journal of Building Engineering. “However, little research has been conducted looking at the impact of which fuel source is used, gas or electric, on achieving low-energy and low-impact goals. We used a unique NIST tool set of databases and software known as BIRDS [Building Industry Reporting and Design for Sustainability] to assess and measure that impact scientifically, and then provide a research method for others to do the same for any climate region in the United States.”
Since its launch in 2014, building experts have used BIRDS to assess and measure the sustainability of the materials as well as energy used by a building throughout its lifespan. Using computer models obtained from BIRDS data, structural engineers, architects, construction managers, and other homebuilding stakeholders can make science-based, economic decisions on how to develop and maintain high-performance, green, and low- or net-zero energy homes.
The new gas-versus-electric fuel source research uses data found in one of the three databases making up the newest version of BIRDS (v4.0), measurements that were acquired from ongoing research at Net-Zero Energy Residential Test Facility (NZERTF) in NIST.
Erected as a prototypical two-story, four-bedroom suburban home on NIST’s campus in Gaithersburg, Maryland, the NZERTF is really a laboratory where NIST scientists and industry partners design, test, and assess the technologies, materials, and strategies that will yield a home that creates at least as much energy as it consumes during the entire year.
To carry out their research, Webb and his colleagues had to develop, via computer modeling, a home grounded on the NIST net-zero concept with an electric HVAC system and a virtual twin that instead used water heating equipment and natural-gas-fired space.
This allowed us to make a true apples-to-apples comparison of gas versus electric for their respective energy, environmental and economic impacts.
Joshua Kneifel, Study Co-Author and Economist, NIST
The scientists compared the two virtual homes as if they were constructed to present-day Maryland codes and regulations for low energy use, added current technology and equipment, and were in the same climate zone as the real NZERTF. Running the models, the software studied 960,000 building design combinations and eight diverse economic situations to estimate performance spanning a time frame of up to 30 years.
Under those criteria, the research results indicate that a natural gas HVAC system is presently more cost-effective in general than an electric one for a code-compliant Maryland residence. Although net-zero energy performance was realized at the least cost using electric heating, it had higher environmental impacts because of the emissions caused during its production.
“The overall economic benefit of natural gas was expected because, at this time, it is the cheaper fuel source in Maryland, costs less in dollars and energy expended to produce and transport, and carries a lower construction price for installation of an HVAC system which uses it,” Webb explained.
However, Kneifel said that electric may still become the better bargain and more environmentally friendly choice.
For example, as more power companies move to cleaner forms of electric generation, such as natural gas instead of coal, the environmental impact will lessen. Also, technology changes, such as cheaper and more efficient solar energy and HVAC systems, should help make the use of electricity more cost-effective.
Joshua Kneifel, Study Co-Author and Economist, NIST
The NIST researchers admit that their sustainability study was narrow with regards to the equipment type, occupant energy demand, and location. They wish other organizations to continue and build on their work to consider numerous key variables. These include the use of substitute equipment such as high-velocity HVAC systems and ground-source heat exchangers, cost and performance in many climates, and changes in building operation that can impact energy consumption rates. Most expressively, they said that future studies must take into consideration improvements in construction materials and methods, technology, and energy production and transmission.